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Kelly and Greta are asked to write an equation for the scenario below:

"One person was able to plant 4 trees in the same amount of time that 5 people working together were able to plant 20 trees."

The girls agree that [tex]x[/tex] represents the number of people working and [tex]y[/tex] represents the number of trees planted. Kelly wrote the equation [tex]y = \frac{1}{4}x[/tex], and Greta wrote the equation [tex]y = 4x[/tex]. Which person is correct, and why?

A. Kelly is correct; each person plants [tex]\frac{1}{4}[/tex] more trees than the person before them.
B. Kelly is correct; [tex]1 = \frac{1}{4} \times 4[/tex] and [tex]5 = \frac{1}{4} \times 20[/tex].
C. Greta is correct; each person plants 4 more trees than the person before them.
D. Greta is correct; [tex]4 = 4 \times 1[/tex] and [tex]20 = 4 \times 5[/tex].


Sagot :

To determine which girl's equation correctly models the given scenario, we need to examine the relationship between the number of people working and the number of trees planted.

The scenario states:
- One person can plant 4 trees.
- Five people working together can plant 20 trees.

Let's check both equations proposed by Kelly and Greta.

Kelly's Equation:
Kelly proposes [tex]\( y = \frac{1}{4} x \)[/tex]
- By substituting [tex]\( x = 1 \)[/tex] (one person), we get [tex]\( y = \frac{1}{4} \times 1 = \frac{1}{4} \)[/tex]. This means one person plants [tex]\(\frac{1}{4}\)[/tex] of a tree, which is clearly incorrect because one person should plant 4 trees.
- By substituting [tex]\( x = 5 \)[/tex] (five people), we get [tex]\( y = \frac{1}{4} \times 5 = 1.25 \)[/tex]. This means five people plant 1.25 trees, which is also incorrect because five people should plant 20 trees.

Therefore, Kelly's equation does not fit the given scenario.

Greta's Equation:
Greta proposes [tex]\( y = 4 x \)[/tex]
- By substituting [tex]\( x = 1 \)[/tex] (one person), we get [tex]\( y = 4 \times 1 = 4 \)[/tex]. This means one person plants 4 trees, which is correct.
- By substituting [tex]\( x = 5 \)[/tex] (five people), we get [tex]\( y = 4 \times 5 = 20 \)[/tex]. This means five people plant 20 trees, which is correct.

Therefore, Greta's equation correctly models the scenario. Greta is correct; each person plants 4 more trees than the person before them. This also matches the specific result [tex]\(4 = 4 \times 1\)[/tex] and [tex]\(20 = 4 \times 5\)[/tex].

Thus, the correct answer is:
Greta is correct; [tex]$4=4 \times 1$[/tex] and [tex]$20=4 \times 5$[/tex].